Recently, a press-fit terminal has been widespread which has a press-fit section connected by its resilient force without implementing solder welding in order for connecting into a through-hole of a substrate etc. Since the press-fit terminal does not need solder welding for connecting to the substrate, thus the connection with the substrate can become easily implemented and the press-fit terminal can be repeatedly attached and detached.
Further, one type of the press-fit terminals is formed by punching a rolled plate with a pressing machine while one type of the press-fit terminals is continuously formed by making use of a wire rod. By employing the press-fit terminal formed of the wire rod, damage of the press-fit terminal can be restricted since the rolling direction of the wire rod during the manufacturing process is in along with the longitudinal direction of the press-fit terminal, thus the press-fit terminal can bear a larger pressing force during the press-fit process to the substrate than the case employing the press-fit terminal formed by punching out from the sheet material.
As a press-fit terminal manufactured from such the wire rod, for example, what is described in the following Patent Document 1 is known. The press-fit pin described in the following Patent Document 1 is a press-fit pin made of a wire material for electrical contacts and is provided with at least one shoulder portion which is integrally formed with the material of the press-fit pin.
According to the press-fit pin disclosed by the following Patent Document 1, the press-fit pin has an advantage in that the press-fit pin can be easily held at the shoulder portion by a press-fitting tool and that there is no need to hold the tip side of the press-fit pin by a press-fitting tool. Further, a force can be more easily transmitted from the press-fitting tool to the press-fit pin in a longitudinal direction without damaging the tip side of the press-fit pin.
Further, the press-fit terminal is formed with a press-fit section which is press-fitted into a through-hole formed on a substrate. This press-fit section is elastically deformed when it is press-fitted into the through-hole, thus dropout prevention is implemented by its resilient force and is connected to the substrate. At this moment, if the resilient force of the press-fit section is small, a sufficient retention force cannot be obtained, thus the connection against the substrate comes to be unreliable and defects such as a conduction failure can occur. On the other hand, if the press-fit section is made in a large size in order to enhance the retention force, it possibly occurs that the substrate is corrupted during the press-fitting. Therefore, there is a need to obtain a sufficient retention force without making the press-fit section so large.
The above Patent Document 2 discloses an invention of a press-fit terminal in which the retention force thereof is enhanced. In the invention of the press-fit terminal disclosed in the above Patent Document 2, when an opening section of the press-fit terminal is formed, a trapezoid depressions which gradually tapered from both sides in thickness direction orthogonal to the deflection direction of an elastic abutment section are press-formed so as to oppose each other by a punch and a die which are faced against each other and have trapezoidal shape in cross section. And thereafter, the bottom of the narrow thin wall part between the depressions is punched out by a press thereby a narrow slit of necessary minimum width for the deflection of the elastic abutment section is formed. According to the invention of the press-fit terminal disclosed in the following Patent Document 2, by the slit being a narrow width, since the height dimension of the elastic abutment section in its deflection direction can be sufficiently ensured, thus the reaction force of the elastic abutment section can be enhanced. Further, the press-fit terminal of the needle eye shape, in general, by ensuring the thickness of the elastic abutment section in its deflection direction, the cross-sectional secondary moment can be increased and the reaction force of the elastic abutment section can be increased, thus the retaining force in the through-hole can be enhanced.